Stationary engines are used in a variety of stationary applications including gas compression, pumping, power generation, and irrigation. Stationary engines can be spark-ignited or compression –ignited (Diesel). Diesel engines inherently operate lean, whereas gasoline engines can be operated in rich or lean condition. The operation of stationary engines results in the emission of criteria air pollutants such as hydrocarbons, volatile organic compounds, carbon monoxide, nitrogen oxides or particulate matter, also in many ventilation systems, stationary catalysts should be used in order to reduction of pollutants.
Behgam offer best emission control technologies especially nanostructure technology for stationary engines which can afford substantial reductions in all of pollutants. However, depending on whether the engine is being run rich or lean and on emission control technology used, the targeted emissions vary as do the levels of control.
In the selective catalytic reduction (SCR) process, NOx reacts with ammonia, which is injected into the flue gas stream before the catalyst. Different SCR catalysts such as vanadium oxide or metal substituted zeolites have different operating temperature windows and must be carefully selected for a particular SCR process. Ammonia-SCR has been used in industrial processes, in stationary diesel engines, as well as in some marine engines. Urea-SCR technology—using urea as the ammonia precursor—has been adapted for mobile diesel engines in both heavy- and light-duty applications.
The SCR technology was first applied in thermal power plants in Japan in the late 1970s, followed by widespread application in Europe since the mid-1980s. In the USA, SCR systems were introduced for gas turbines in the 1990s, with a growing number of installations for NOx control from coal-fired powerplants.
Since mid-2000s, urea-SCR technology has been also adopted for mobile diesel engines. The mobile engine application required overcoming several problems related to the urea dosing technology, catalysts optimization, as well as urea infrastructure. Ultimately, SCR proved to be a more robust emission technology than the main alternative option, NOx adsorbers, and has been widely used in all types of mobile diesel engines. In the United States, SCR systems were introduced by most engine manufacturers in 2010, to meet the US EPA NOx limit of 0.2 g/bhp-hr for heavy-duty engines.
The SCR process requires precise control of the ammonia injection rate. An insufficient injection may result in unacceptably low NOx conversions. An injection rate which is too high results in release of undesirable ammonia to the atmosphere. These ammonia emissions from SCR systems are known as ammonia slip.